Windows Guest Instances Have No Sound

### problem

Windows guest instances (Virtual Desktops) do not find any Audio hardware.

By adding `sound` to the global setting `allow.additional.vm.configuration.list.kvm`...

...CloudMonkey can add this `extraconfig`.

Then, after power cycling the VM, the issue is resolved.

It does not feel like a feature request, but a "bug" to the default global settings.